title: Hydrodynamical properties of recombinant spider silk proteins: Effects of pH, salts and shear, and implications for the spinning process.
abstract: We have investigated the effect of pH, salts and shear on the hydrodynamical diameter of recombinant major ampullate (MA) rMaSpI silk proteins in solution as a function of time using (1) H solution NMR spectroscopy. The results indicate that the silk proteins in solution are composed of two diffusing populations, a high proportion of "native" solubilized proteins and a small amount of high molecular weight oligomers. Similar results are observed with the MA gland content. Salts help maintaining the proteins in a compact form in solution over time and inhibit aggregation, the absence of salts triggering protein assembly leading to a gel state. Moreover, the aggregation kinetics of rMaSpI at low salt concentration accelerates as the pH is close to the isoelectric point of the proteins, suggesting that the pH decrease tends to slow down aggregation. The data also support the strong impact of shear on the spinning process and suggest that the assembly is driven by a nucleation conformational conversion mechanism. Thus, the adjustment of the physicochemical conditions in the ampulla seems to promote a stable, long term storage. In addition, the optimization of protein conformation as well as their unfolding and aggregation propensity in the duct leads to a specifically organized structure.
authors.affiliation: Department of Chemistry, Regroupement québécois de recherche sur la fonction, la structure et l'ingénierie des protéines (PROTEO), Centre de recherche sur les matériaux avancés (CERMA), Université Laval, Québec, QC G1V 0A6, Canada.
authors.forename: Jérémie
authors.initials: J
authors.lastname: Leclerc
authors.forename: Thierry
authors.initials: T
authors.lastname: Lefèvre
authors.forename: Martin
authors.initials: M
authors.lastname: Gauthier
authors.forename: Stéphane M
authors.initials: SM
authors.lastname: Gagné
authors.forename: Michèle
authors.initials: M
authors.lastname: Auger
mesh_terms: D000818:Animals; D060829:Arthropod Proteins; D006863:Hydrogen-Ion Concentration; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry; D047011:Silk / Q000737:chemistry; D013112:Spiders / Q000737:chemistry
chemical_list: D060829:Arthropod Proteins; D011994:Recombinant Proteins; D047011:Silk